This invention relates to fastener driving tools and, more particularly, to portable fastener driving tools having pressure valving permitting the tool to operate remotely.
The type of portable fastener driving tool hereto contemplated typically includes a fastener driving element or driver which is mounted within a drive track within which successive fasteners are fed. The driver is mounted for movement through repetitive cycles, each of which includes a drive stroke during which the fastener is moved out of the drive track into the work piece and a return stroke. The fastener driving element is fixedly connected with a piston which is mounted within a cylinder for movement through a drive stroke and a return stroke with the fastener driving element. The piston is driven by compressed air applied to an operative surface of the piston. Generally, actuating of the tool occurs upon manually actuating a trigger valve.
There are certain circumstances when it is desirable to actuate the tool remotely. One approach to remote tool actuation is to provide a pneumatic cylinder and a sling secured to the trigger. The cylinder moves the sling vertically which moves the trigger. This type of device is used for slow applications and is often used with a contact trip arm. In operation, the cylinder is retracted and the tool is lowered. When the contact trip comes into contact with the work surface, the tool is cycled. An advantage of this arrangement is that no modification of the tool is required, but a major disadvantage is that the arrangement increases the cost of components, has slow cycle rates and higher maintenance costs.
Another method of remote cycling a tool is to remove the hand operated trigger valve and replace it with a hollow plug. The plug is coupled to a normally opened 3-way solenoid or pilot operated signal valve. The advantage to this arrangement is low cost, no tool modification and the requirement of only a few parts. A disadvantage of this arrangement is that a large volume of air must be exhausted through the normally opened 3-way valve, thus not allowing the tool to perform at its peak cycle rate.